260 



and Phillipsburgh, along with B. Saffordi, but is not so common as that 

 species. 



In a blue limestone, evidently belonging to the Calciferous formation at 

 Comstock, in the State of New York, numerous specimens of the glabella 

 of a trilobite, which can scarcely be distinguished from B. Cordai, have 

 been collected. 



Bathydrus Nero. (N. sp.) 



Pig. 243. 



Fig. 243. — Bathyxirus Nero, a, upper aide of the glabella; b, side view of a specimen, 

 with an arched outline ; c and d, pygidia. 



Description. — Oblong-ovate, about three inches in length and two in 

 width. Head strongly convex, with the posterior angles produced back- 

 wards into long stout spines. Glabella oblong, a httle wider in front than 

 at the neck segment ; sides nearly straight and sub-parallel ; well defined 

 all round by the dorsal furrows ; strongly convex or semi-cylindrical ; 

 abruptly elevated in front ; the outline, on a side view, nearly straight, 

 with the exception of the front, or gently arched as in fig. h; neck furrow 

 concave, rather deep, extending all across ; neck segment rounded, well de- 

 fined. Pygidium semi-elliptical, strongly convex, broadly rounded behind ; 

 front margin slightly convex ; length a little greater than half the width ; 

 axis very convex, about four fifths the length and a little less than one third 

 the width of the pygidium ; obtusely rounded and abruptly elevated at the 

 apex, with five strong transverse rings ; sides with four ribs, besides the 

 half rib at the front margin ; these ribs are, in small specimens, divided 

 or simply forked by a groove, for half their length next the margin; in 

 large specimens the groove becomes deeper, and crosses the rib obliquely 

 from behind, forwards and outwards, leaving a large tubercle next the axis 

 in front, and another behind the groove, near the margin. 



The whole of the surface, so far as yet observed, is covered with strong 

 tubercles. 



No entire specimens have been seen ; but the detached cheeks, found 

 in the same hand specimens of rock, show that the posterior angles of the 

 head are spmose, as above mentioned. 



